Currently, all commercially available silicon-based thin film solar cells are produced using plasma enhanced chemical vapor deposition (PECVD) coating tools. However, the inventors have observed that PECVD processes suffer from various undesirable limitations, such as: low process gas utilization (for example, about 3% to 20%); poor layer uniformity; introduction of plasma or charge induced defects in the deposited films or in the substrates themselves; deposition is static due to electrical grounding requirement; scaling-up is difficult because of RF requirements; high system cost; low deposition rate (for example, approximately 0.5 nm/s for silicon); and deposition chambers are cleaned using NF3 (a greenhouse gas).
Although HWCVD deposition processes are potentially suitable for silicon thin film deposition in manufacturing (see, for example, Matsumura et al., Thin Solid Films 516(5) 537-540 (2008)), the inventors have observed that there are no robust manufacturing deposition tools suitable to realize the full manufacturing potential of HWCVD sources for silicon thin film deposition on large substrates.
Thus, the inventors have provided a processing system that integrates HWCVD sources into a robust manufacturing deposition tool that is suitable to enhance the manufacturing potential of HWCVD sources for silicon thin film deposition on large substrates. Embodiments of the inventive processing system provide deposition systems for fabrication of silicon-based thin film solar cells that may have one or more of the following benefits: more efficient, lower cost, high throughput, and more readily scalable. Embodiments of the present invention may also be utilized in the fabrication of other thin film devices such as thin film batteries, polymer devices, flexible photovoltaic devices, and flexible electronics.